### Brain Teasers

# Principal Witnesses

The Principal of Jimbo's school interviewed 30% of the 8th graders at recess about the food fight yesterday. The Assistant Principal grabbed 40% of 8th graders at lunchtime to investigate the disappearance of all of the blackboard erasers. Fortunately for Jimbo, he was in the 50% of 8th graders that escaped without an interview. If twenty-five 8th graders had to front only the Principal, how many students are in 8th grade at Jimbo's school?

### Answer

Since 50% had no interview, then 50% did have an interview. But the Principal and the Assistant P together interviewed 40% + 30% = 70%. That means 20% of the 8th graders were interviewed twice. That leaves 10% who fronted only the Principal. Thus there are 250 students in 8th grade at Jimbo's school.Hide Answer Show Answer

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## Comments

Another great one (and I got to use a Venn diagram, which is really breaking out some old school solving techniques...)

Gotta watch that wording. I got 83.33333... Which is 25/3*10

Same effect, but it seemed more natural to me:

There were only 50%-40% = 10% of the interviewed students who didn't face the assistant principal.

Not even sure that one even took a whole three seconds.

There were only 50%-40% = 10% of the interviewed students who didn't face the assistant principal.

Not even sure that one even took a whole three seconds.

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